1. Field of the Invention
The present invention relates to a film antenna, and more particularly, to a film antenna integrally formed with a mobile communication terminal case.
2. Description of the Related Art
Mobile communication terminals including global positioning systems, personal digital assistants, cellular phones, wireless notebook computers and the like are required to be further miniaturized recently as they are widely used more than ever before. In order to meet such a demand, the focus has been placed on reducing the volume of the terminals while retaining diverse functions of the terminals. This applies also to antennas, which is an essential part of the mobile communication terminals.
In general, among different kinds of antennas of the mobile communication terminals, external antennas such as rod antennas and helical antennas extend in a certain length from exteriors of terminals, limiting miniaturization and portability of the terminals. In addition, they are likely to be damaged when the mobile communication terminals are dropped.
On the other hand, internal antennas mounted inside mobile communication terminals, such as surface-mounted chip antennas, have a reduced risk of damage but limit miniaturization of the terminals due to their physical size.
Therefore, there has been introduced a method of forming a radiator of the antenna directly in a terminal case or on an antenna base, effectively utilizing a space.
FIG. 1A is a perspective view illustrating a conventional internal antenna for a mobile communication terminal, and FIG. 1B is a sectional view illustrating the conventional internal antenna mounted in a mobile communication terminal.
Referring to FIG. 1A, a base 11 of plastic material and a radiator 13 in a form of a metal plate with a pattern formed thereon are manufactured by injection molding and pressing, respectively, and integrated afterwards by fusion bonding.
However, in such a method, a basic space is required inside a terminal for mounting the antenna, limiting miniaturization of the terminal.
In this case, the radiator 13 may be formed on the base 11 by printing a conductive ink. However, since the antenna base is formed of a plastic material, the work of forming the radiator 13 on the base 11 should be conducted at a certain temperature or lower, which does not bring about deformation of the plastic material. Therefore, the antenna pattern formed on the base may be printed by using a low-temperature paste, which is limited in selection with factors to be considered, such as printability and adhesion property.
In addition, the conductive ink includes conductive and organic substances for printability and adhesion property. In this case, the organic substances may be eliminated from the conductive ink when the conductive ink is treated at high temperatures but may remain in the conductive ink when the conductive ink is treated at low temperatures. With the antenna base formed of a polymer-based material, it is not suitable to treat the conductive ink at high temperatures, and thus, the organic substances tend to remain in the conductive ink even after the radiator of the antenna is completed. This may lead to degradation of electric conductivity, which is the most important property of the radiator of the antenna, eventually causing deterioration of radiation characteristics of the antenna.
Furthermore, printing the conductive ink on a three-dimensional antenna base is a difficult operation.